About the OpenBuilds Lead Screw Customization.

There is a very small reduction in diameter to make it easier to insert into the nut blocks. It tells you in the link you posted - the diameter is 7.8 mm.

Alex.

 

Good evening.
I’m currently assembling an OpenBuilds LEAD 1515. Today I assembled the Y-axis actuators. One of the lead screws was very tight, but I did manage to get it installed.

The other was much tighter. Impossible to turn with my hands. I got some rubber gloves, still couldn’t turn it. Tried putting two tension nuts on the end in a “jam-nut” configuration and turning it that way. Didn’t work. Finally, I sprayed some dry-lube on the screw threads and in the nut block. Then I was able to turn it with the rubber gloves on, but only barely and with tremendous effort. It took a long time.

When squaring the gantry (step 23 in the build video, I think), in order to move the gantry to front of machine on that side, I had to rotate the screw by using a 13mm open end wrench on the tension nut. The other screw rotated by hand with no problem.

I have two points here:
1: Despite “customization, the screw/nut block was just too tight in this case. Tight is good, but immovable is not.
2: I hope it operates properly when completed. Having to disassemble back to this point and reassemble with another screw would be highly frustrating. Having to disassemble even further back to replacing the nut block would be significantly worse. I will spray all the screws with dry-line before I boot it up and jog it for the first time.

Thx, rink.

 

Arghhh! Potential disassembly. Blah.
But I suppose better now than when it’s completely assembled.

I didn’t use a torque wrench, but I’d estimate about 4 ft/lbs required to turn that screw. I’ll let someone else translate that into stepper motor language.

Think the nema 23 high-torque motor would turn it ok?

 

A battery drill probably will - I assume you are talking about unscrewing it for disassembly.
Alex.

 

Alex,
Actually I was wondering if the stepper motor would turn it in normal use. But I doubt it would. Just too tight.

And being that much tighter than the other one, I would worry about calibration and accuracy issues.

On tap for today was to install the X-axis lead screw. I’ll try that one as well before contacting the store.

 

I tried the X-axis and same problem. The lead screw just spins against the hole in the delrin nut block. I have to push very hard to get the threads to engage. When they do engage, then I can’t turn the screw any further.

With a CNC being a “precision” tool, I would have thought these would be manufactured to very tight tolerances and even checked for fit before leaving the factory. I’m a little surprised.

I sent a note to http://support.openbuilds.com/support/home

 

I thought about using teflon tape but was concerned about making a high and low side because of the wrap. I used some heat shrink tubing to take up the dead space and it seems well centered. The heat shrink will also "unthread" if I heat it up and need to take it off. At the end of the day I would still rather spin the lead screw in a drill and sand the end to get it to interference fit into the end support bearing.

 

David, Good evening.
Yes, sir.
That post was from a couple months ago.
I did get them from OpenBuilds, as part of the LEAD 1515 Fully Loaded package.

I contacted support, they sent me new ones. In the end, I threaded each nut block onto the lead screw individually, making sure to space them appropriately. Then I fastened the nut blocks to the gantry plate. It was difficult since the gantry plate assemblies were already completed and installed on the v-slot extrusions. But with some blue tape and some fiddling I finally got it all together.

I feel like the nut block threads should be calibrated to start/stop such that you can thread the lead screw through one and then it catches the start of the other one while both blocks are in their fixed (slightly loose) positions. Mine definitely were not calibrated that way. I tried backing the lead screw off and restarting it multiple times, tried from the other end, tried jiggling the slightly loose nut blocks…but they just wouldn’t synch.

Anyway, up and running now and I love it.

Thx, rink.